The Importance of the Canonical Wnt Signaling Pathway in the Porcine Endometrial Stromal Stem/Progenitor Cells: Implications for Regeneration.

The regenerative ability of the endometrium is strongly associated with the presence of adult stem/progenitor cells. Purposes of the present study were (1) to establish the presence of stem/progenitor cells in porcine endometrial stroma using a clonogenic assay and (2) to investigate whether the canonical Wnt pathway affects the potential of stem/progenitor cells to undergo self-renewal or differentiation. The utility of endometrial stromal clones as a model for stem/progenitor studies was evaluated based on these cells' increased expression of mesenchymal stem cell (MSC) marker genes, including CD29, CD73, CD90, and CD105, compared with primary cultured cells. Small molecules were introduced to activate (BIO) or inhibit (XAV939) the canonical Wnt pathway during stromal clone formation. Cloning efficiency assays revealed that activation of the Wnt/β-catenin pathway promoted formation of more differentiated small clones. Moreover, activation of the Wnt/β-catenin pathway decreased, whereas inhibition of the pathway increased MSC marker expression. Additionally, we confirmed the importance of canonical Wnt pathway stimulation in endometrial stromal cells through observing the appropriate changes in β-catenin cellular localization. These data indicate that modulation of the canonical Wnt pathway effects the process of regeneration in the porcine endometrium during the course of the estrous cycle.